If you’re planning an air tightness assessment or working toward Part L compliance, you’ve likely come across the term blower door test. But what exactly is it?
Put simply, a blower door test is another name for an air tightness test — they both describe the same method of assessing how much air leaks through a building’s fabric. It’s a key part of demonstrating that a building meets energy efficiency standards under UK Building Regulations.
What Is a Blower Door Test?
A blower door is a piece of calibrated testing equipment. It includes a fan mounted into a temporary frame that fits snugly into a main doorway. During the test, the fan pressurises and depressurises the building, while instruments measure airflow to calculate the air permeability rate — the volume of air leakage per hour per square metre at 50 Pascals (m³/h·m² @ 50 Pa).
While it’s a term more commonly used in the United States, it’s increasingly recognised in the UK construction and building compliance sector as another name for an air tightness test. Both terms refer to the same method of assessing how much air escapes from a building through unsealed gaps and junctions.
This is the standard method of testing required for demonstrating compliance with Approved Document Part L. The results feed into SAP or SBEM calculations to determine overall energy performance.
Want to Learn More?
For in-depth guidance on air tightness and how to prepare for a test, check out the following articles:
- What Is Air Tightness Testing?
A foundational overview of how the test works and why it matters. - How to Prepare for a Building Air Tightness Test
Practical steps to get your site ready and avoid delays. - Why Buildings Fail Air Tightness Tests
Common issues and how to address them before retesting. - Air Tightness Testing Services
Everything we offer — from diagnostics to certification.
Book a Blower Door Test with ATS
At Air Tightness Solutions, we perform certified blower door tests across the UK for domestic and commercial projects. Our expert team helps you understand the process, prepare properly, and pass your test with confidence.
If you’re ready to schedule a blower door test, or have questions about compliance, get in touch with us. You can also explore our full building compliance services if you need a more comprehensive package.